Physicochemical Aspects of Microemulsion Flooding

Abstract

ABSTRACT Whenever water, an oil and a surfactant equilibrate at concentrations of surfactant in excess of critical micelle concentrations, one or more microemulsions form. In view of this, all surfactant flooding processes may involve microemulsions in situ. Ternary diagrams have been constructed for three specific microemulsion systems showing the effects of salinity and cosurfactant on phase behavior, viscosity, resistivity, optical birefringence and interfacial tension. Using these data, micellar structure maps were prepared for the single phase region. In this connection, Winsor's concept of intermicellar equilibrium was found consistent with microemulsion systems of interest for tertiary oil recovery. Experimental techniques are described for minimizing extent of the multiphase region and measuring low interfacial tensions that obtain there. INTRODUCTION General Considerations It is sometimes difficult to sort out the multiplicity of terminology concerning various kinds of micellar solutions and the structural states in which they. exist. For example, Schulman introduced the term micro emulsion. Winsor2 objects on the grounds that all emulsions are unstable and a microemulsion must be some kind of an emulsion. Tosch, et al.3 use the phrase "micelle-containing solutions" whereas Shinoda and Kunieda4 prefer "swollen micellar solution." Nevertheless, the term microemulsion is convenient, is in common use, and it is only necessary to understand precisely what is meant by the term.